Spark plug shield



y 15, 1951 J. w. SAILLER 2,553,114

SPARK PLUG SHIELD Filed Oct. 25, 1946 mmvron. HN W c9A/LLER F WW ATTORNEYS.

Patented May 15, 1951 UNITED STATES PATENT OFFICE SPARK PLUG SHIELD Application October 25, 1946, Serial No. 705,572

9 Claims.

This invention relates to a shield or protector for spark plugs of the type employed for operation of internal combustion engines.

An object of the invention is to provide a shield for effectively preventing short circuiting of a spark plug, and to provide a shield which can be readily applied to such plug, removed therefrom to accommodate servicing and re-applied.

The conventional design of spark plug includes a shell threaded into and grounded on the engine cylinder head and carrying one of the electrodes, an insulator core which projects above the shell, and a central second electrode extending through the shell and core, with the upper end terminating beyond the core end and the lower terminating adjacent the electrode carried by the shell. The upper end of the central electrode detachably receives a current conducting wire and for efficient operation it is necessary to concentrate the intensity of the spark at the gap between the electrodes. Inasmuch as a considerable portion of the core projects beyond the shell, the surface thereof is exposed to moisture and may accumulate a film or coating of foreign matter and as a result the current instead of moving in the normal path to the gap at the electrodes will be short circuited over the exposed surface of the insulator to the shell.

An object of the invention, therefore, is to so protect the exposed surface of the insulator as to prevent by-passing of the current thereover and for this purpose I employ an assembly of components of non-conducting material, one thereof being resiliently deflectible, preferably of rubber or a rubber-like material, and the other relatively rigid, perferably a molded plastic material. Such components are relatively constructed and arranged to effect snug, sealing engagement therebetween and with the spark plug components through the inherent resiliency of the material of the rubber component, and in this respect the relatively rigid component may deflect the rubber, as by compression thereof to effect snug, sealing engagement therebetween and to effect such engagement of the rubber component with the spark plug insulator.

Other objects and advantages of the invention will be more apparent from the following description taken in connection with the accompanying drawings, in which:

Fig. l is an elevational view, partly in section, showing a spark plug and the shield applied thereto.

Fig. 2 is a sectional elevational view of the resilient component of the shield.

Fig. 3 is a view similar to Fig. 1 but showing a further embodiment of the shield.

Referring to the drawings, the shield is illustrated as applied to a spark plug of the type now commonly used for operation of internal combustion engines and which includes a metallic shell 5 threaded at the lower end thereof for application to the engine cylinder head in the well known manner, such shell carrying one of the electrodes 6. A second electrode 1 extends through the shell 5 and has a contact point at its lower end in spaced relation to the electrode 6, the space therebetween constituting the spark gap across which the current flashes. The upper end of the electrode 1 has an enlarged screw threaded portion on which is threaded a relatively elongated nut 8 to which a current conducting wire 9 is detachably connected. An insulator or core ID of porcelain or other non-conducting material has a central bore receiving the electrode 1 and projects upwardly from and terminates beyond the shell 5 but short of the upper terminal of the electrode I. The upper end of the insulator or core is sealed as at l l.

The shield as embodied in Figs. 1 and 2 includes a resilient member [2 of rubber or a like material centrally apertured to receive the insulator or core [0, the diameter of such aperture initially corresponding to the diameter of the core so that the wall of the central aperture will snugly fit and sealingly engage the external surface of the core. The lower end face of the member [2 seats on the upper end face of the shell 5 and is recessed to overlap the latter and thus can provide a seal at the seat by relatively lightly pressing member I2 against the end face of shell 5. The upper end of member l2 has a portion l3 reduced in diameter relative to the main body and a flange or shoulder M at the juncture of the latter and portion [3, the external surface of the latter being tapered in the direction of the free end thereof. The member l2 may be formed by molding a body of rubber or like material.

Coacting with the member 12 in forming the shield is a relatively rigid hollow member [5 of non-conducting material such as a molded plastic body.

The member [5 has an aperture [6 in the top wall thereof to receive the top terminal of electrode 1 and extends over the exposed end of insulator core l0 and downwardly and outwardly therefrom to telescope with the reduced portion [3 of member I2 and having an internal surface shaped to generally correspond to the surface of portion l3 and to snugly fit the same, preferably 3 by forcing the member I5 downwardly. The snug fit provides a seal between the lower extremity of member I5 and member I2 which may be augmented by engagement of the free edge of member I5 with the shoulder I4 of member I2. Force fitting of member I5 onto the surface of the portion I3 will tend to exert a compressive force on the material of member I2 in the region of such reduced portion and cause the latter to more snugly engage the insulator or core than otherwise.

The above arrangement provides a shield which completely encloses the projected part of the insulator or core I and thus the surface thereof is no longer exposed to moisture and the accumulation of foreign matter thereon. Withthe surface so protected the tendency to short circuiting is reduced to a minimum. In assembly, the wire 9 and nut 8 are removed, the spark plug inserted through the central aperture of member I2 and the latter pressed against the end face of the shell 5, themember l being then assembled by inserting the top electrode terminal through opening I6 and pressing the member I5 downwardly, and thereafter threading nut 8 in place, the latter retaining the member l5 in press fit engagement with the member I2 as aforesaid. This assembly may bemade when the spark plug is positioned in the cylinder head or removed therefrom. Reference is made to my copending application, Serial No. 181,183, filed August 28, 1950, as a division of this application and which more particularly discloses and claims among other things the member I2 apart from other features of the invention claimed herein.

Referring to Fig.3, the shield includes the relatively rigid member I5 and a member I! of resiliently yieldable material, such as rubber, which is aperturedat I8 to receive the top terminal of electrode I and which extends over the upper end of insulator or core If! and downwardly around the latter, having an internal diameter so related to the diameter as to snugly fit the external surface of the core by reason of the inherent resiliency of the material. The member I'I extends below an annular bead I8 on the core Ill and terminates in a relatively enlarged portion I9 defining an annular bead, the internal surface of which snugly fits the core I0 and the external surface of which engages the internal surface of the member I5, the latter extending downwardly beyond the bead I9 but terminating short of the shell 5. Preferably the bead l9 has a diameter sufficiently large so that the material of the bead is compressed in the final assembly thereby forming a snug, sealing engagement between the members I5, I1 at the bead I9 and further augmenting the snug sealing fit between the internal surface of bead E9 and external surface of core I0. 7 I

The shield may be assembled, with the spark plug either removed or in place in the cylinder head, by removing the nut 8 and wire 9, installing the member II, then member I5 and nut 8,

the latter retaining the member I5in the snug tting engagement with bead I9 as aforesaid.

I claim:

1. A shield adapted for detachable application to a spark plug including a shell, an insulator having a part thereof including an end extended beyond the shell and an electrode having a terminal beyond the insulator end, said shield including a relatively rigid hollow member aperoutwardly therefrom, and a member of rubberlike material apertured for receiving said insulator and having a face at one end thereof engageable with said shell, said rubber-like member having a portion of reduced diameter adapted to extend into said rigid member, said rubberlike member having a wall thickness at said end suflicient that a portion of said face will project outwardly from said shell to locate the entire outer periphery of said end in outwardly spaced relationship to the shell when the rubber-like member is applied to the plug.

2. A shield adapted for detachable application to a spark plug including a shell, an insulator having a part thereof including an end extended beyond the shell and an electrode having a terminal beyond the insulator end, said shield intured to receive saidterminal and adapted toextend over the insulator end and downwardly and eluding a relatively rigid hollow first member apertured to receive said terminal and adapted to extend over the insulator end and downwardly and outwardly therefrom but to terminate short of said shell, and a second member of rubberlike material apertured for receiving and snugly engaging the peripheral surface of said insulator intermediate the said end thereof and said shell, said members being dimensioned for fitting said first member over at least a portion of said second member and said first member having a tapered and regular internal surface having compressive engagement with the said portion of said second member when fitted thereon.

3. A shield adapted for detachable application to a spark plug having a shell, an insulator having a part thereof including an end extended beyond the shell,and an electrode having a terminal beyond the insulator end, said shield including a first member of rubber like material apertured to receive said terminal and adapted to extend over said insulator end and downwardly therefrom around said insulator part, said first member being so dimensioned as to snugly engage with said insulator part intermediate said end and said shell, and a relatively rigid hollow second member apertured for receiving said terminal and adapted to extend over said insulator end and downwardly therefrom around said first member and to snugly engage the latter.

4. A shield adapted for detachable application to a spark plug having a shell, an insulator having a part thereof including an end extended beyond the shell, and an electrode having a terminal beyond the insulator end, said shield including a first member of rubber-like material apertured to receive said terminal and adapted to extend over said insulator end and downwardly therefrom around said insulator part, said first member being so dimensioned as to engage with said insulator part intermediate said end and said shell and having an external annular bead at the portion the-reef adapted to engage said insulator part, and a relatively rigid hollow second member apertured for receiving said terminal and adaptedto extend over said insulator end and downwardly therefrom around said first member to overlap and engage said bead, said bead having a diameter sufficiently large relative to the internal diameter of said second member as to be compressed by the latter into snug fitting engagement therewith and to force said first member into snug engagement with said insulator part as aforesaid.

5. A spark plug having a shell, an insulator projecting above the shell and an electrode projecting from an end of the insulator, and a shield including a relatively -rigid hollow first member having an end extending over the insulator end and an opening at the end receiving said electrode, said member extending downwardly around said insulator and having a second end terminating short of the shell, said shield including a second member of rubber-like material having an opening therethrough receiving said insulator and a first part extending into said first member in snug fitting engagement therewith and a second part extending between the second end of the first member and said shell and seated on the latter in sealing engagement therewith, said second part extending outwardly beyond the second end of said first member and the outermost periphery of said shell.

6. A spark plug having a shell, an insulator projecting above the shell and an electrode projecting from an end of the insulator, and a shield including a relatively rigid hollow first member having an end extending over the insulator end and an opening at the end receiving said electrode, said member extending downwardly around said insulator and having a second end terminating short of the shell, said shield including a second member of rubber-like material having an opening therethrough receiving said insulator and a first part extending into said first member in snug fitting engagement therewith and a second part extending between the second end of the first member and said shell and seated on the latter in sealing engagement therewith, said second part extending outwardly beyond the second end of said first member and the outermost periphery of said shell, said second member at the juncture of its said parts including an annular wall extending from the outer periphery of said first part and beneath the second end of said first member.

7. A spark plug having a shell, an insulator projecting above the shell and an electrode projecting from an end of the insulator, and a shield including a relatively rigid hollow first member having an end extending over the insulator end and an opening at the end receiving said electrode, said member extending downwardly around said insulator and having a second end terminating short of the shell, said shield including a second member of rubber-like material having an opening therethrough receiving said insulator and a first part extending into said first member, said first part and said first member including tapered regular surfaces disposed in snug fitting engagement, said second member having a second part extending between the second end of the first member and said shell and seated on the latter in sealing engagement therewith, said second part extending outwardly beyond the second end of said first member and the outermost periphery of said shell.

8. A spark plug having a shell, an insulator projecting above the shell and an electrode projecting from an end of the insulator, and a shield including a relatively rigid hollow first member having an end extending over the insulator end and an opening at the end receiving said electrode, said member extending downwardly around said insulator and having a second end termi nating short of the shell, said shield including a second member of rubber-like material having an opening therethrough receiving said insulator and a first part extending into said first member in snug fitting engagement therewith and a second part extending between the second end of the first member and said shell and having an end face, a portion of which is engaged with said shell, said end face extending outwardly beyond the outermost periphery of said shell.

9. A spark plug having a shell, an insulator projecting above the shell and an electrode projecting from an end of the insulator, and a shield including a relatively rigid hollow first member having an end extending over the insulator end and an opening at the end receiving said electrode, said member extending downwardly around said insulator and having a second end terminating in spaced relation to the shell, said shield including a member of rubber-like material closing the space between the second end of said first member and said shell and having an opening therethrough receiving said insulator and an end adjacent said shell, the entire outer Deriphery of said second member at its said end being disposed outwardly beyond the outermost periphery of said shell.

JOHN W. SAILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 868,737 Watt Oct. 22, 1907 1,191,162 Dixon July 18, 1916 1,306,304 Herz June 10, 1919 1,794,673 Creager Mar. 3, 1931 2,044,325 Patock June 16, 1936 2,190,765 Barr Feb. 20, 1940 2,253,220 Andres Aug. 19, 1941 2,269,076 Boll Jan. 6, 1942 2,436,712 Burrell et al. Feb. 24, 1948 

